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| United States Patent |
5,767,034
|
|
Diaz-Barrios
, et al.
|
June 16, 1998
|
Olefin polymerization catalyst with additive comprising aluminum-silicon
composition, calixarene derivatives or cyclodextrin derivatives
Abstract
An olefin polymerization catalyst includes a halogen-containing magnesium
compound; a titanium compound; and an additive selected from the group
consisting of (a) a mixture of an aluminum alkoxide compound and
polydimethylsiloxane, (b) an aluminosiloxane, (c) the reaction product of
an aluminum alkyl and a calixarene, (d) the reaction product of an
aluminum alkyl and a cyclodextrin, and mixtures of (a)-(d).
| Inventors:
|
Diaz-Barrios; Antonio (San Antonio, VE);
Liscano; Jose (Los Teques, VE);
Trujillo; Marianela (Caracas, VE);
Agrifoglio; Giuseppe (Caracas, VE);
Matos; Jose Orlando (Los Teques, VE)
|
| Assignee:
|
Intevep, S.A. (Caracas, VE)
|
| Appl. No.:
|
656028 |
| Filed:
|
May 31, 1996 |
| Current U.S. Class: |
502/132; 502/103; 502/118; 502/125; 502/126; 502/129 |
| Intern'l Class: |
B01J 031/00; B01J 037/00; C08F 004/02; C08F 004/60 |
| Field of Search: |
502/104,108,118,129,132
|
References Cited
U.S. Patent Documents
| 396932 | Jul., 1889 | Gloriod et al. | 502/103.
|
| 3629216 | Dec., 1971 | Iwasaki et al. | 502/117.
|
| 3661878 | May., 1972 | Aishima et al. | 502/132.
|
| 3987233 | Oct., 1976 | Sato et al. | 502/129.
|
| 4027089 | May., 1977 | Aishima et al. | 502/116.
|
| 4036867 | Jul., 1977 | Piekarski et al. | 502/103.
|
| 4069169 | Jan., 1978 | Toyoda et al. | 252/441.
|
| 4290915 | Sep., 1981 | Toyota et al. | 526/125.
|
| 4315088 | Feb., 1982 | Kitagawa et al. | 502/132.
|
| 4324877 | Apr., 1982 | Ueno et al. | 502/132.
|
| 5075270 | Dec., 1991 | Brun et al. | 502/117.
|
| 5137995 | Aug., 1992 | Yokoyama et al. | 502/125.
|
| 5192732 | Mar., 1993 | Duranel et al. | 502/126.
|
| 5212133 | May., 1993 | Duranel et al. | 502/125.
|
| 5238891 | Aug., 1993 | Miro | 502/113.
|
| 5354721 | Oct., 1994 | Geerts | 502/117.
|
| 5411925 | May., 1995 | Geerts et al. | 502/117.
|
| 5414180 | May., 1995 | Geerts et al. | 502/117.
|
| 5439662 | Aug., 1995 | Spitz et al. | 502/107.
|
| 5455018 | Oct., 1995 | Brun et al. | 502/134.
|
| 5484754 | Jan., 1996 | Spitz et al. | 502/117.
|
Other References
Scata' et al., US Reissue 31,099 of USP 4,115,319, issued Sep. 1978, Dec.
1982.
|
Primary Examiner: Caldarola; Glenn
Assistant Examiner: Pastwozyk; J.
Attorney, Agent or Firm: Bachman & LaPointe, P.C.
Claims
What is claimed is:
1. An olefin polymerization catalyst, comprising:
a halogen-containing magnesium compound;
a titanium compound; and
an additive selected from the group consisting of
(a) a mixture of an aluminum tri-alkoxide compound and
polydimethylsiloxane,
(b) an aluminosiloxane selected from the group consisting of ›Al(OR').sub.2
(OSiR".sub.3)!.sub.m, ›Al(OR')(OSiR".sub.3).sub.2 !.sub.p, and
›Al(OSiR".sub.3).sub.3 !.sub.2, wherein R' and R" are alkyl or aryl groups
having up to 12 carbons and .sub.m and .sub.p are any whole number greater
than 1,
(c) the reaction product of an aluminum alkyl and a calixarene,
(d) the reaction product of an aluminum alkyl and a cyclodextrin, and
mixtures of (a)-(d).
2. A catalyst according to claim 1, wherein said catalyst has a
substantially monomodal particle size distribution having an average
particle size of between about 2 microns and about 200 microns.
3. A catalyst according to claim 1, wherein said magnesium halide comprises
MgCl.sub.2 and wherein said titanium compound comprises TiCl.sub.4.
4. A catalyst according to claim 1, wherein said additive contains aluminum
and silicon and has an Al/Si molar ratio of between about 0.33 and about
1.
5. A catalyst according to claim 4, wherein said additive has an Al/Si
molar ratio of between about 0.33 and about 1.
6. A catalyst according to claim 1, wherein said catalyst has a Ti/Al molar
ratio of between about 10 and about 100.
7. A catalyst according to claim 1, wherein said catalyst has an Mg/Al
molar ratio of between about 10 and about 600.
8. A catalyst according to claim 1, wherein said additive comprises a
mixture of said aluminum tri-alkoxide compound and said
polydimethylsiloxane, and wherein said polydimethylsiloxane has a
molecular weight of between about 150 and about 300,000.
9. A catalyst according to claim 8, wherein said aluminum tri-alkoxide
compound is an organic compound having the functionality
##STR2##
wherein R, R' and R" are hydrocarbyl radicals of not more than 12 carbon
atoms.
10. A catalyst according to claim 8, wherein said aluminum tri-alkoxide
compound is selected from the group consisting of aluminum methoxide,
aluminum ethoxide, aluminum isopropoxide and mixtures thereof.
11. A catalyst according to claim 8, wherein said polydimethylsiloxane has
a molecular weight of between about 150 and about 770.
12. A catalyst according to claim 1, wherein said additive is selected from
the group consisting of (c) the reaction product of an aluminum alkyl and
a calixarene, (d) the reaction product of an aluminum alkyl and a
cyclodextrin, and mixtures of (c) and (d).
13. A catalyst according to claim 12, wherein said additive results from
reaction of a calixarene selected from the group consisting of
4-tert-butylcalix›4!arene, 4-tert-butylcalix›6!arene,
4-tert-butylcalix›8!arene, and mixtures thereof.
14. A catalyst according to claim 12, wherein said additive results from
reaction of a cyclodextrin selected from the group consisting of
.alpha.-cyclodextrin, .beta.-cyclodextrin, .gamma.-cyclodextrin, and
mixtures thereof.
15. A catalyst according to claim 1, wherein said additive comprises an
aluminosiloxane compound.
16. A catalyst according to claim 15, wherein said aluminosiloxane compound
is selected from the group consisting of ›Al(O.sup.i Pr).sub.2
(OSiMe.sub.3)!.sub.m, ›Al(O.sup.i Pr) (OSiMe.sub.3).sub.2 !.sub.p,
›Al(OSiMe.sub.3).sub.3 !.sub.2, and mixtures thereof, wherein .sub.m and
.sub.p are any whole number greater than 1.
17. A catalyst according to claim 1, wherein R' is selected from the group
consisting of ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl and
mixtures thereof, and wherein R" is selected from the group consisting of
methyl, phenyl, ethyl, propyl, isopropyl, t-butyl and mixtures thereof.
Description
BACKGROUND OF THE INVENTION
The invention relates to a polymerization catalyst, particularly to a
polymerization catalyst for the polymerization of olefins.
Numerous processes are known in the art for polymerization of olefins such
as ethylene into polyolefins such as polyethylene.
Parameters of concern during the polymerization of olefins include the
yield of polyolefin, the melt flow index (MFI) of the polyolefin product,
the bulk density of the polyolefin product, and the content of fines in
the resulting polyolefin product. Numerous catalysts and processes are
known in the art for polymerizing olefins so as to obtain polyolefins. The
need remains, however, for a polymerization catalyst for polymerization of
olefins which has good activity toward the polymerization reaction, while
providing a final product with a desirable melt flow index and bulk
density, and further while reducing the content of fines therein.
It is therefore the primary object of the present invention to provide a
polymerization catalyst for polymerization of olefins which has enhanced
activity toward the polymerization reaction so as to provide enhanced
yield of polyolefin product with a desirable bulk density.
It is a further object of the present invention to provide an olefin
polymerization catalyst wherein the polyolefin product has a reduced
content of fines.
It is a further object of the present invention to provide an additive for
an olefin polymerization catalyst which enhances the characteristics of
the catalyst for polymerization of olefins.
Other objects and advantages of the present invention will appear
hereinbelow.
SUMMARY OF THE INVENTION
In accordance with the present invention, the foregoing objects and
advantages are readily attained. In accordance with the invention, an
olefin polymerization catalyst is provided which comprises a
halogen-containing magnesium compound; a titanium compound; and an
additive selected from the group consisting of (a) a mixture of an
aluminum alkoxide compound and polydimethylsiloxane, (b) an
aluminosiloxane, (c) the reaction product of an aluminum alkyl and
calixarene, (d) the reaction product of an aluminum alkyl and cyclodextrin
and mixtures of (a)-(d).
BRIEF DESCRIPTION OF THE DRAWINGS
A detailed description of preferred embodiments of the invention follows,
with reference to the attached drawings, wherein:
FIG. 1 illustrates a cyclodextrin additive component for use in accordance
with an embodiment of the invention;
FIG. 2 illustrates a calixarene additive component according to a further
embodiment of the invention; and
FIGS. 3-7 illustrate alternative embodiments of aluminosiloxane additives
according to the present invention.
DETAILED DESCRIPTION
The invention relates to an olefin polymerization catalyst, especially to a
catalyst for polymerization of olefins such as ethylene into polyolefins
such as polyethylene.
The present polymerization catalyst is based upon Ziegler-Natta catalysts
typically comprising a magnesium halide support and a titanium compound
supported on the magnesium halide support. In accordance with the present
invention, a series of additives have been developed which, when
incorporated into the polymerization catalyst, provide enhanced activity
and characteristics of the catalyst toward the polymerization reaction. In
accordance with the invention, it has been found to be advantageous to
incorporate an additive selected from the group consisting of (a) a
mixture of an aluminum alkoxide compound and polydimethylsiloxane, (b) an
aluminosiloxane, (c) the reaction product of an aluminum alkyl and
calixarene, (d) the reaction product of an aluminum alkyl and
cyclodextrin, and mixtures thereof so as to provide the olefin
polymerization catalyst according to the present invention. A catalyst
containing such an additive according to the present invention has been
found to have excellent activity toward the polymerization reaction so as
to provide an enhanced yield of polyolefin having desirable qualities,
while using a relatively small amount of titanium, and further while
providing a catalyst which results in a reduced amount of fines in the
resulting polyolefin product.
In accordance with the invention, the halogen containing magnesium compound
may suitably be magnesium chloride, while the titanium compound may
suitably be titanium chloride, especially titanium tetrachloride.
As set forth above, the series of additives which has been found in
accordance with the invention to provide desirable characteristics in a
polymerization catalyst includes an additive selected from the group
consisting of (a) a mixture of an aluminum alkoxide compound and
polydimethylsiloxane, (b) an aluminosiloxane, (c) the reaction product of
an aluminum alkyl and calixarene, (d) the reaction product of an aluminum
alkyl and cyclodextrin, and -mixtures thereof.
One additive in accordance with the present invention, as set forth above,
may suitably be a mixture of aluminum compound and polydimethylsiloxane.
An aluminum alkoxide compound as used herein refers to an organic compound
having the functionality
##STR1##
wherein R, R' and R" are the same or different hydrocarbyl radicals of not
more than 12 carbon atoms, such as methyl, ethyl, isopropyl and the like.
Examples of particularly desirable aluminum alkoxide compounds for
combination with polydimethylsiloxane in accordance with the invention
include aluminum methoxide, aluminum ethoxide, aluminum isopropoxide and
mixtures thereof.
In accordance with the present invention, when the additive is to be a
mixture of aluminum alkoxide and polydimethylsiloxane, the
polydimethylsiloxane preferably has a molecular weight of between about
150 and about 300,000, more preferably between about 150 and about 770.
Relatively low molecular weight polydimethylsiloxane has been found in
accordance with the invention to provide a catalyst having a better
catalyst activity than those produced with higher molecular weight
polydimethylsiloxane.
As set forth above, preferred additives for the catalyst in accordance with
the present invention include calixarene and/or cyclodextrin compounds.
Referring to FIG. 1, a cyclodextrin compound is illustrated which is
suitable in accordance with the present invention for reaction with an
aluminum alkyl, and the reaction product thereof is suitable for
incorporation as an additive into an olefin polymerization catalyst so as
to provide enhanced characteristics with respect to the desired process.
Examples of suitable cyclodextrin compounds include .alpha.-cyclodextrin,
.beta.-cyclodextrin, .gamma.-cyclodextrin and mixtures thereof.
Referring to FIG. 2, an example of a calixarene compound which upon
reaction with an aluminum alkyl, the reaction product thereof is suitable
as an additive in accordance with the present invention is shown.
Calixarene compounds have been found in accordance with the present
invention to enhance the activity of a polymerization catalyst for the
polymerization of olefin when the reaction product between a calixarene
and an aluminum alkyl is added as an additive. Examples of suitable
calixarene compounds include calix›4!arene, calix›6!arene, calix›8!arene,
4-tert-butylcalix›4!arene, 4-tert-butylcalix›6!arene,
4-tert-butylcalix›8!arene and mixtures thereof.
Specific examples of suitable aluminum alkyl compounds include
trimethylaluminum, triethylaluminum, tri-i-butylaluminum and mixtures
thereof.
In further accordance with the invention, aluminosiloxane compounds have
also been found to be particularly desirably additives to the catalyst in
accordance with the present invention. The aluminosiloxane compound in
accordance with the present invention is preferably selected from the
group consisting of ›Al(OR').sub.2 (OSiR".sub.3)!.sub.m,
›Al(OR')(OSiR".sub.3).sub.2 !.sub.p, and ›Al(OSiR".sub.3).sub.3 !.sub.2,
wherein R' and R" are alkyl or aryl groups, preferably having up to about
12 carbons and m and p are any whole number greater than 1. R' may
preferably be selected from the group consisting of ethyl, propyl,
isopropyl, n-butyl, isobutyl, t-butyl and mixtures thereof, while R" is
selected from the group consisting of methyl, phenyl, ethyl, propyl,
isopropyl, t-butyl and mixtures thereof. The organo aluminosiloxy compound
according to the invention has a ratio of Al:Si which is preferably 1:1,
1:2, or 1:3.
As set forth above, one preferable form of the organo aluminosiloxy
compound is ›Al(OR').sub.2 (OSiR".sub.3)!.sub.m. Two examples of this
compound are shown in the drawings in FIGS. 3 and 4. In the example
illustrated in FIGS. 3 and 4, R' is isopropyl, R" is methyl, and the ratio
of Al:Si is 1:1.
Referring to FIG. 5, another preferred organo aluminosiloxy compound is
shown which corresponds to ›Al(OSiR".sub.3).sub.3 !.sub.2, as set forth
above. As shown in FIG. 5, R" in this compound is methyl, and the ratio
Al:Si is 1:3.
Referring to FIGS. 6 and 7, a further embodiment of an organo aluminosiloxy
compound additive in accordance with the present invention is shown. In
accordance with the illustrated embodiment, compounds are illustrated
having the formula ›Al(OR')(OSiR".sub.3).sub.2 !.sub.p. In the embodiment
shown in FIGS. 6 and 7, R' is isopropyl, while R" is methyl, and the ratio
Al:Si is 1:2.
The olefin polymerization catalyst of the present invention preferably has
a substantially monomodal and narrow particle size distribution which
preferably has an average particle size of between about 2 microns to
about 200 microns. Further, the catalyst preferably has an Al/Si molar
ratio of between about 0.1 to about 300, more preferably between about
0.33 to about 1 (Al:Si between 1:1 to 1:3), especially when the additive
is an aluminosiloxane compound.
Further, the catalyst according to the present invention preferably has a
molar ratio Ti/Al of between about 10 to about 100, and a molar ratio
Mg/Al of between about 10 to about 600.
In accordance with the invention, the additive of the present invention may
suitably be added to the catalyst ingredients during synthesis of same.
Alternatively, the additive of the present invention may suitably be
incorporated into the catalyst composition, before or during olefin
polymerization.
In accordance with the invention, the desired additive may be prepared
through numerous different methods.
In connection with the aluminosiloxane compound additive, the preparation
thereof may be accomplished according to K. Folting, W. E. Streib, K. G.
Caulton, O. Poncelet and L. G. Hubert-Pfalzgraf, Polyhedron, 10 (14),
1639-1646 (1991). A mixture of trimethylsilylacetate and cyclohexane may
be added to aluminum isopropoxide in the desired ratio so as to provide
the desired relation of Si:Al of 1:1, 2:1 or 3:1. The mixtures so formed
are then subjected to azeotropic distillation so as to obtain
cyclohexane/isopropylacetate, and the solution can then be concentrated
and distilled so as to provide the desired additive. Azeotropic
distillation may be carried out at a temperature of approximately
80.degree. C. and for a time period of between about 8 to about 24 hours.
Of course, the time and temperature of the procedure may be adjusted to
particular conditions and ingredients. The resulting additive product may
suitably be identified and confirmed to possess the desired structure
through IR and .sup.1 H NMR spectroscopies.
An aluminosiloxane compound ›Al (O.sup.i Pr).sub.2 (OSiMe.sub.3)!.sub.m
according to the invention has spectroscopic information as follows:
IR(cm.sup.-1): 1250(Si--C); 1180, 1130 (C--CH.sub.3); 1070; 950 (Si--O);
760; 640 (Al--OR).
.sup.1 H NMR (CDCl.sub.3 ; 0.1M, 25.degree. C.) (ppm): 4.47-4.08 (m,
OCHMe.sub.2, 2H). 1.42; 1.27; 1.47; 1.36; 1.21; 1.10; 1.06 (d, J=6Hz,
OCHMe.sub.2, 12H); 0.25, 0.22, 0.21 (s, OSiMe.sub.3, 9H).
Alternatively, for example when the additive is to be a calixarene or
cyclodextrin compound, a solution of trimethylaluminum in toluene may be
added to a suspension of a calixarene or cyclodextrin reactant and
anhydrous toluene, preferably while stirring in a cold bath for a
sufficient period of time, such as approximately 2 hours. The temperature
of the mixture is then increased or allowed to reach room temperature, and
additional stirring is carried out. A solid is eventually obtained, after
evaporation of solvent under a vacuum, and the resulting calixarene or
cyclodextrin additive compound can be characterized by IR and/or NMR
spectroscopies. Such an additive will typically exhibit spectroscopies as
follows:
IR(cm.sup.-1): 2900-2850, 1510, 1380, 1290 (C--H); 600 (Al--OR).
.sup.1 H NMR (CDCl.sub.3 ; 0.1M, 25.degree. C.) (ppm): 7.0 (m, H, Ar); 3.3
(m, Ar--CH.sub.2 --Ar); 1.0 (m, CMe.sub.3); -1.1 (M, Al--Me).
While the foregoing provide examples for preparation of additive in
accordance with the present invention, it should of course be noted that
other processes for preparation of the desired additive may be known to
those of ordinary skill in the art and could, of course, be used to
prepare the additive of the catalyst of the present invention.
In further accordance with the invention, a catalyst can be prepared
through a synthesis method wherein a mixture of a halogen-containing
magnesium compound such as magnesium chloride, a C.sub.4 -C.sub.12
aliphatic or aromatic solvent such as decane, a C.sub.6 -C.sub.12
aliphatic or aromatic alcohol such as 2-ethylhexanol and the desired
additive is formed. The mixture is preferably charged into a reactor
vessel under an inert gas atmosphere, and reacted at an elevated
temperature such as approximately 110.degree.-140.degree. C. for a period
of time of approximately 1-4 hours, preferably under stirring. The
reaction mixture may then in accordance with the present invention be
cooled, preferably to between about 0.degree. C. to about -20.degree. C.,
and a volume of titanium halide such as titanium tetrachloride is slowly
added. An additional charge of the desired additive is then added to the
mixture, and the mixture is continuously stirred for an additional time
period. The mixture is then heated again to an elevated temperature
between 60.degree.-100.degree. C., for a period of time of 1 to 3 hours,
cooled to room temperature and then allowed to settle, and is separated by
filtration.
The separated solid is then preferably suspended in a solution of titanium
tetrachloride, heated for another period of time, and resulting solid is
again separated for example by filtration. The solid so obtained is then
purified, for example by repeated washing with hot hexane, and is then
dried under vacuum or inert gas stream. The resulting catalyst is in
powder form and preferably has a titanium content of between about 3 to
about 12 wt. %, and an average particle size of between about 4 to about
100 microns.
In accordance with the present invention, the above-described process for
synthesis has been found to provide catalyst having improved activity.
Nevertheless, other methods are of course known in the art for the
synthesis of such catalysts, and the catalyst of the present invention
could be prepared by such known methods.
The olefin polymerization catalyst of the present invention can suitably be
used for olefin polymerization reactions so as to produce polyolefins such
as polyethylene, including any related polymers and the like.
A polymerization reactor may suitably be subjected to evacuation-argon
substitution, and then charged with dehydrated and oxygen-removed hexane
as well as triethylaluminum and hydrogen so as to prepare the reactor. The
reactor may then be saturated with olefins such as ethylene at a working
pressure and temperature, for example 8 bar and 80.degree. C., and the
catalyst according to the present invention may then be charged into the
reactor. After a suitable amount of time, such as, for example, 2 hours,
the resulting polymer slurry can be filtered, and a yield of polyolefin
such as polyethylene is produced. In accordance with the invention, the
polyolefin product preferably has a melt flow index of between about 0.01
to about 200, and a bulk density of between about 0.25 to about 0.40.
Further, the polymerization according to the present invention using the
catalyst of the present invention preferably results in the final
polyolefin product having a fines content of less than or equal to about
15% of particles having a diameter of less than or equal to about 106
microns.
Methods for preparing the additive of the present invention, for preparing
the catalyst of the present invention including such additive, and for
using the catalyst of the present invention in polymerization reactions
have been discussed above. It should of course be noted that numerous
alternatives to these methods could be carried out by a person of ordinary
skill in the art so as to prepare and/or use the catalyst within the scope
of the present invention.
The following examples further illustrate preparation of additive and
catalyst and polymerization in accordance with the invention.
EXAMPLE 1
The preparation of an aluminosiloxane additive of the formula ›Al(O.sup.i
Pr).sub.2 OSiMe.sub.3 !.sub.m was carried out in accordance with the
aforementioned reference by K. Folting et al., wherein .sup.i Pr is
isopropyl and Me is methyl. A solution of trimethylsilyl acetate (3.165 g,
0.024 mol) in 0.65 ml of cyclohexane was added to aluminum triisopropoxide
(4.93 g, 0.024 mol) over a period of two hours at a temperature of
80.degree. C. whereby azeotropic distillation of cyclohexane/isopropyl
acetate was achieved. The solution so obtained was then concentrated and
distilled at 80.degree. C. and 0.01 mm Hg so as to provide additive A, the
composition of which was confirmed by IR and .sup.1 H NMR spectroscopies.
Two additional additives were also prepared following the same procedures,
but altering the Al:Si ratio so as to provide two additional additives:
›Al(O.sup.i Pr)(OSiMe.sub.3).sub.2 !.sub.p (Additive B); and
›Al(OSiMe.sub.3).sub.3 !.sub.2 (Additive C).
The preparation of a catalyst in accordance with the invention using
additive A as prepared above was then carried out. 12.00 g of anhydrous
magnesium chloride, 100 ml of decane, 60 ml of 2-ethyl hexanol and 0.25 g
of Additive A were charged under an inert gas atmosphere into a reactor
vessel and reacted at 120.degree. C. for 2 hours. The reaction mixture was
cooled to -20.degree. C. and then 200 ml of titanium tetrachloride were
slowly added. The mixture was stirred for an additional period of 30
minutes, and the temperature of the mixture was then increased to room
temperature with occasional stirring and another 0.125 g of additive A
were added, after which the mixture was stirred for an additional 30
minutes.
The mixture was heated to 90.degree. C. for 2 hours and the resulting solid
was allowed to settle, was separated by filtration, suspended in 60 ml of
titanium tetrachloride and heated at 80.degree. C. for 2 hours. The solid
was separated by filtration, repeatedly washed with a total volume of hot
hexane of about 1000 ml and finally dried under vacuum. The resulting
yellow powder showed a titanium content of 8.2% and an average particle
size of 14 microns.
EXAMPLE 2
This example illustrates a polymerization reaction using the catalyst
according to the present invention as prepared above in Example 1. A
stainless steel autoclave having a stirrer, a temperature controlling
device and a 2 liter capacity was provided. The reactor was subjected to
evacuation-argon substitution several times and was charged with 1 liter
of dehydrated and oxygen-removed hexane, 1.68 mmol of triethyl aluminum
and 3 bar of hydrogen. The reactor was saturated with ethylene at the
working pressure of 8 bar and at 80.degree. C., and approximately 10 mg of
the catalyst of Example 1 containing additive A were charged into the
reactor. Polymerization was carried out for 2 hours, at which time the
resulting polymer slurry was filtered. The process yielded 340 g of
polyethylene having a melt flow index of 0.5 g/10 min and a bulk density
of 0.25 g/ml. The product had a content of 1.7% of fines having a diameter
of less than 106 microns.
EXAMPLE 3
This example illustrates polymerization carried out according to the
invention using a catalyst prepared according to the process of Example 1
using 0.725 g of additive B instead of the 0.125 g of additive A. The
resulting catalyst was a yellow powder having a titanium content of 7.7
wt. % and an average particle size of 11.1 microns.
Ethylene was polymerized according to the same procedure set forth in
Example 2, using the catalyst including additive B, and the polyethylene
yield was 346 g having a melt flow index of 0.57 g/10 min and a bulk
density of 0.25 g/ml. The final product contained 2.63% fines having a
diameter of less than 106 microns.
EXAMPLE 4
This example illustrates the preparation of a calixarene additive (Additive
D), as well as the preparation and use of a catalyst including this
additive.
A solution of trimethylaluminum (3.7 ml, 0.038 mol) in 30 ml of toluene was
added dropwise to a suspension of 500 mg of 4-tert-butylcalix›8!arene in
30 ml of anhydrous toluene. The reaction was conducted with magnetic
stirring in a cold bath at -76.degree. C. Upon completion of the alkyl
solution addition, the reaction mixture was allowed to reach room
temperature and further stirred for 1 hour. Evolution of gas was observed
during the process. A white solid was obtained after evaporation of the
solvent under vacuum. The resulting additive product was characterized by
IR and NMR spectroscopies as follows: IR: (cm.sup.-1) 2900-2850, 1510,
1380, 1290 (C--H); 600 (Al--Or).
.sup.1 H NMR (CDCl.sub.3 ; 0.1M, 25.degree. C.) (ppm): 7.0 (m, H, Ar); 3.3
(m, Ar--CH.sub.2 --Ar); 1.0 (m, CMe.sub.3); -1.1 (m, Al--Me).
EXAMPLE 5
A catalyst was prepared similarly to that of Example 1 above, adding 6.00 g
of anhydrous magnesium chloride, 50 ml of decane, 30 ml of 2-ethylhexanol
and 1.00 g of additive D, (as prepared in Example 4) and charging the
mixture into a reactor vessel under inert gas conditions. The mixture
reacted vigorously with gas evolution at room temperature. After this, the
reactor was heated to 150.degree. C. for 3 hours. The resulting solution
was cooled to -20.degree. C. and then 100 ml of titanium tetrachloride
were slowly added for a period of 1.5 hours. This solution was allowed to
reach room temperature and a further 0.70 g of additive D suspended in 20
ml of decane were added. The mixture was heated at 90.degree. C. for 2
hours, the supernatant liquid was discarded, and the solid was treated
with 30 ml of titanium tetrachloride and heated to 80.degree. C. for 2
hours. The solid was collected by filtration, repeatedly washed with hot
hexane using a total volume of about 600 ml, and dried under a vacuum. The
resulting reddish-brown powder showed a titanium content of 7.7% and an
average particle size of 18 microns.
The catalyst prepared as above was then used in a polymerization reaction
under the same conditions as set forth above in Example 2. After 1 hour of
polymerization, the yield of polyethylene was 182 g with a melt flow index
of 0.76 g/10 min and a bulk density of 0.27 g/ml. The final product
contained 12.8% fines having a diameter of less than 106 microns.
EXAMPLE 6
This example illustrates the preparation of a cyclodextrin additive
(Additive E), as well as the preparation and use of a catalyst including
this additive.
A solution of trimethylaluminum (1.5 ml, 0.016 mol) in 30 ml of toluene was
added dropwise to a suspension of 1.00 g of .beta.-cyclodextrin (which had
been previously dried by heating under vacuum) in 40 ml of anhydrous
toluene. The reaction was conducted with magnetic stirring in a cold bath
at -76.degree. C. Upon completion of the alkyl solution addition, the
reaction mixture was allowed to reach room temperature and further stirred
for 48 hours. A white solid was obtained after evaporating the solvent
under vacuum. The resulting product (additive E) was characterized by IR,
.sup.1 H NMR and .sup.13 C NMR spectroscopies as follows:
IR (cm.sup.-1): 2900-2850, 1510 (C--H); 1120-980 (C--O); 770-600 (--OR)
(Al--OR).
.sup.1 H NMR (CDCl.sub.3 ; 0.1M, 25.degree. C.) (ppm): 3.5(s, H, O--CH--O);
-0.8 (s, Al--Me).
A catalyst was then prepared following a similar process to that discussed
in Example 1. 6.00 g of anhydrous magnesium chloride, 50 ml of decane, 30
ml of 2-ethylhexanol and 1.225 g of additive E, as prepared above, were
charged under inert gas conditions into a reactor vessel. The mixture
reacted vigorously with gas evolution at room temperature. After this, the
reactor was heated at 150.degree. C. for 3 hours. The resulting solution
was cooled to -20.degree. C. and then 100 ml of titanium tetrachloride
were slowly added for a period of 1.5 hours. This solution was allowed to
reach room temperature and a further 1.225 g of additive E, suspended in
20 ml of decane, were added. The mixture was heated at 90.degree. C. for 2
hours, then the supernatant liquid was discarded while the solid portion
was treated with 30 ml of titanium tetrachloride and heated at 80.degree.
C. for 2 hours. The solid was collected by filtration, repeatedly washed
(total volume of hot hexane used for washing=600 ml), and dried under
vacuum. The resulting yellow powder contained 8.0% by weight of titanium
and had an average particle size of 8.4 microns.
The catalyst prepared above was then used in a polymerization reaction as
follows. Ethylene was polymerized under the same conditions as in Example
2 using the catalyst component above described. After 2 hours of
polymerization, the yield of polyethylene was 154 g with a melt flow index
of 1.27 g/10 min and a bulk density of 0.29 g/ml. The final product
contained 0.3% of fines having a diameter of less than 106 microns.
This invention may be embodied in other forms or carried out in other ways
without departing from the spirit or essential characteristics thereof.
The present embodiment is therefore to be considered as in all respects
illustrative and not restrictive, the scope of the invention being
indicated by the appended claims, and all changes which come within the
meaning and range of equivalency are intended to be embraced therein.
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